Cylinder construction



Patented July 29, i947 UNITED STATES ATENT OFFICE Gloucester, England, assignors to Rotol Limited, a British company Application September 25, 1942, Serial No. 459,686 In Great Britain June 20, 1941 Claims.

This invention concerns cylinder construction for Variable-pitch airscrews of the hydraulicallyoperated type in which the mechanism for altering the pitch of the blades is a double-acting hydraulic ram mounted in front of the airscrewhub. The hydraulic mechanism consists essentially of a stationary piston carried by a hollow shaft coaxially with the air screw-hub, and a cylinder which is movable on said piston, the cylinder being further supported by a tubular extension which is arranged to encircle the shaft aforesaid which carries the piston and slide within the hollow bore of the airscrew-shaft.

It is the object of this invention to provide a construction of cylinder and its associated parts which affords great economy in materialand in manufacture; it will be appreciated that since it is desirable that any parts associated with an airscrew should be of a minimum weight, the material used has to be of high quality and disposed in such manner as to take the best advantage of its strength. If the various parts are machined from forgings, there is a very considerable waste of high-grade materialwhich involves transport charges for the raw material and for the scrap material; in addition, the scrap high-grade steel cannot be recovered as such so that consequential losses are involv d in the manufacture of the high-grade steel.

According to this invention, a hydraulic control mechanism of the type described comprises a cylinder formed as a pressing domed at one end and having a radial flange at the other open end, a cylinder-cover bolted to the cylinderflange, and supporting a tubular extension 1 formed integrally with or secured to the cylindercover at its central opening.

According to another feature of this invention, a hydraulic cup-packing is provided at the joint of the cylinder and cover with its open side facing the interior of the cylinder. The open side of the cup-packing may be directed at an angle of, say, 45 to the cylinder axis. For this purpose, the cylinder-flange, according to another feature of this invention, is connected to the cylinder wall by a conical portion; the cylindercover may be formed with an annular V-shaped groove registering with the conical portion of the cylinder, to provide the channel for the hydraulic packing. This arrangement of the hydraulic packing inclined to the cylinder-axis is beneficial in that it enables the flanges to be made thinner than they would be if the packing were made either parallel with or at right-angles to the cylinder-axis and it also permits a reduction in the overall diameter with a consequent reduction in weight. This arrangement also provides a shaping of the parts which is particularly appropriate for production by pressing and retaining the maximum strength of the parts concerned.

A cylinder constructed in accordance with this invention will now be described, by Way of example only, with reference to the accompanying drawings, in which:

Figure 1 is an axial section through the cylinder and connected parts,

Figure 2 is a side elevation of a bracket attached to the cylinder, partly in section, and

Figures 3, 4 and 5 show details of the cylinder construction.

The cylinder ill is formed by a deep drawing process with a domed end ll having a central flanged opening 12 in it. This opening I2 is useful in the forming process, and is also necessary in the finished product in which it is closed by a screw-threaded plug !3. The open end of the cylinder has a radial flange M which is connected to the wall of the cylinder by a short conical portion l5 inclined at 45 to the axis of the cylinder. This shaping is advantageous in that it facilitates the distribution of the metal in the drawing operation and preserves a regular grain flow so that the strength of the cylinder and flange is maintained at its maximum. The open end of the cylinder is closed by a cylinder-cover It which is preferably formed by a pressing operation as a dished conical plate having a flat annular flange I8 and a central flanged hole IT. The cover is bolted to the cylinder by bolts 33 through the mating flanges l8 and I4. Two annular ridges l9 and 2B are formed in the inner edge of the flange 18 of the cover during the pressing operation and are V-shaped in section of comparatively small height so that the regular grain flow can be maintained in their formation. One side of the outer ridge [9 abuts the inner surface of the conical portion l5 of the cylinder and the ridges provide between them a V-shaped annular groove or notch to complete, with the conical portion I5 of the cylinder, an annular channel of rectangular cross-section to receive a hydraulic cup-packing 2|. It will be observed that th necessary depth of the channel for the packing ring 2! is obtained without it being necessary to increase the thickness of the flange l8 and without weakeningthe cover by the formation of a deep groove in it.

A tubular extension 22 is fabricated separately and is secured to the cylinder-cover at 23 by butt-welding. The cover is formed with a flange providing a flared portion 24 to which the extension 22 is attached by the simplest form of butt-weld. If, however, it is more convenient in manufacture, the flared portion 24 may be formed on the extension, by upsetting, instead of on the cover, or partly in each part.

In order to simplify the manufacture of the cylinder H3, its flange Hi may be formed as a separate element by suitable pressing and machining operations and butt-welded to it at the line indicated at 35 in Figure 1. Figures 3, 4 and 5 show successive stages in such operations, starting with an annular plate in Figure .3 of substantially the required thickness of the flange M. This enables an adequate thickness of flange to be provided, in combination with a thin walled portion which is butt-welded to the cylinder shelf and ensures the maximum strength of the material by providing a suitable grain-flow.

The cylinder reciprocates, in use, on a fixed piston which is carried on the end of a hollow fixed shaft that passes through the tubular extension 22 and a sealin bearing is provided between the extension 22 and the hollow shaft on which it slides. This bearing is a bush 25 of any suitable plastic or synthetic resin or light alloy pressed or moulded in the extension 22.

"In use the cylinder is operatively connected to each airscrew blade by a separate linkage and each linkage includes a bracket 23 having an internally screw-threaded tubular portion 21 to receive a link-bolt 28. One end of the link bolt is slit at 29 to receive one end of a connecting rod which is articulated to the link-bolt by a pin passed through a hole 30. The other end of the link-bolt is reduced in diameter at 3| and is engaged in suitable accurately positioned holes in the flanges M and 18 so as to locate both the link accurately on the cylinder-cover and the latter relatively to the cylinder. The bracket is held on the cylinder by bolts 32 (Figure 2) and these bolts and the bolts 33 can be so positioned as to clear the cylinder and need not be accurately fitted. The link-bolt must be adjusted about its axis to bring the slot 29 into the correct plane, and axially to bring the hole 30 to the correct position so that the bolt will mate with the connecting rod. This is done by screwing the link-bolt into the bracket until slot 29 is in the correct plane and the bolt is adjusted axially, to its correct position within half the pitch of its threads. The axial adjustment is completed by the insertion of a shim-'34 (Figure2) between the bracket and the flange is of the cover and the thickness of this shim need not exceed the pitch of the thread on the link-bolt. The axial adjustment of the link-bolts provides for the finepitch adjustment of the airscrew blades.

It will be seen that this invention provides a construction which is particularly advantageous in that it is light in weight but of adequate strength and which can be produced with the maximum economy both in material and in the manufacturing processes.

The cylinder it reciprocates in a well known manner upon a stationary piston within the cylinder but inasmuch as such stationary piston forms no part of the present invention it is omitted for clearness. Such pistons are illustrated in the Patents 1,829,930 dated November 3, 1931, and 2,332,786 dated October 26, 1943.

We claim:

1. A cylinder, for use in a hydraulic control mechanism of the kind described, formed as a pressing domed at one end and having a radial flange around its other open end and an outwardly flared conical portion joining the radial flange to the cylinder wall, a cylinder-cover bolted to the cylinder flange and formed with an annular V-shaped groove to register with the conical portion of the cylinder and provide a channel along the joint between the cylinder and the cover and a hydraulic cup-packing in the said channel.

2. A cylinder, for use in a hydraulic control mechanism of the kind described, formed as a pressing domed at one end open at the other and formed with an outwardly-flared conical portion at its open end and an external radial flange at the outer end of the conical portion, a cylinder-cover bolted onto the flange of the cylinder and formed as a pressing with a central opening and a pair of concentric annular V- shaped ridges on its inner surface whereof the outer surface of the outer ridge abuts the inner surface of the conical portion of the cylinder and the inner surface of the outer ridge, the outer surface of the inner ridge and the inner surface of the conical portion of the cylinder define a channelof rectangular cross-section, and a hydraulic cup-packing in the said channel,

3. A cylinder, for use in a hydraulic control mechanism of the kind described, formed as a pressing domed at one end having an externally flanged opening centrally disposed in it and formed with a radial flang around its other open end, a plug for closing the opening in the domed end of the cylinder, a cylinder-cover formed as a pressing with a central opening and bolted on the cylinder flange, a tubular extension buttwelded round the opening in the cylinder-cover.

4. A cylinder, for use in a hydraulic control mechanism of the kind described, formed as a pressing with one end domed and the other end open and surrounded by an external radial flange, a cy-li-ndercover formed as a pressing with a central opening and bolted onto the cylinder flange, a tubular extension butt-Welded at one end to the cylinder-cover around the opening therein, and a sealing bush of a plastic material formed in the tubular extension adjacent its welded end.

5. A cylinder construction, for use in a hydraulic control mechanism of the kind described, comprising a cylinder formed as a pressing with one end domed and the other end open and surrounded by an external radial flange, a cylindercover formed as a pressing with a central opening and bolted around its periphery to the cylinder flange, a tubular extension welded to the cylinder-cover around its central opening, a bracket bolted to the cylinder-cover adjacent its periphery and formed with an internally threaded tubular portion, and a link-bolt screwed into the tubular portion of the bracket and having its outer end shaped for articulation to a connecting rod.

6. The combination according to claim 5, in which the inner end of the link-bolt is reduced in diameter and fits snugly within a hole accurately formed in the cylinder-cover.

7. A cylinder construction, for use in a hydraulic control mechanism of the kind described, comprising a cylinder formed as a pressing with one end domed and the other end open and formed with an outwardly-flared conical portion around its open end and with an external radial flange at the larger end of the conical portion, a cylinder-cover bolted around its periphery to the cylinder flange and formed as a pressing with a central opening and with an annular V-shaped notch registering with the conical portion of the cylinder to provide a channel along the joint between the cylinder and cover, a hydraulic cup-- packing in the said channel, a tubular extension butt-welded to the cover around its central opening, a number of brackets bolted to the cover and equally spaced around its periphery, each of which :brackets has an internally screw-threaded tubular portion, a separate link-bolt screwed into each extension and formed with a reduced inner end fitting snugly within an accurately positioned hole in the cylinder-cover and with its outer end shaped for articulation to a connecting rod.

8. A cylinder for use in hydraulic control mechanism of the kind described comprising a cylindrical container having a pressed dome at one end and a radial flange around its other open end, a cover for said cylinder comprising a wall with a central opening and having a radial flange, said cover flange being formed with an annular V-shaped groove to receive a packing along the joint between the cylinder and cover, and means joining said cylinder and cover at their flanged portions.

9. A cylinder for use in hydraulic control mechanism comprising a cylinder formed as a pressing with one end domed and the other end open and formed with an outwardly flared conical portion around its open end, .an external radial flange welded around the larger end of the conical portion, a cylinder cover bolted around its periphery to the cylinder flange, said cover formed as pressing with a central opening and with an annular V-shaped notch registering with the conical portion of the cylinder to provide a channel along the joint between th cylinder'and cover, a cup-packing in said channel obliquely disposed to the cylinder axis, and a tubular extension welded to the cover around its central opening.

10. A device of the kind described comprising a cylinder having a cylindrical wall with an outwardly domed outer end formed in one piece with the cylinder wall, said cylinder wall and domed end both being of light weight and strong con struction, said cylinder wall having an outturned flange at its inner open end with a short conical portion between such flange and the cylinder end, a removable cover for the inner end of the cylinder having a flange to mate with the cylinder flange, a pair of annular spaced ridges on the interior of the cover adjacent the cover flange, such annular ridges being substantially V-shaped in cross section and providing one Wall at right angles to said short conical portion of the cylinder and a second wall in parallel spaced relation from said short conical portion, said short conical portion and said two walls of the annular ridges forming an annular packing space substantially rectangular in cross section with its side walls diagonal to the axis of the cylinder, said space being open toward said cylinder, and a hydraulic cup packing in said annular space with its open side toward the open portion of the space to communicate with internal cylinder pressure.

ROBERT HENRY COVEERltEY. DAVID DUNDAS ARNOTT.

REFERENCES CITED The following references are of record in the 7 file of this patent:

UNITED STATES PATENTS Number Name Date 475,585 Locke May 24, 1892 1,236,816 Behan Aug. 14, 1917 2,632,254 Caldwell Feb. 25, 1936 1,829,930 Hale-Shaw Nov. 3, 1931 2,332,786 Fairhurst Oct. 26, 1943 2,239,613 Martin Apr. 22, 1941 2,209,032 Mott July 23, 1940 2,280,341 Mott Apr. 21, 1942 1,598,137 Jacobson Aug. 31, 1926 1,440,349 Foltz Dec. 26, 1922 1,278,184 Maegly Sept. 10, 1918 1,618,412 Dorward Feb. 22, 1927 631,661 Perry Aug. 22, 1899 FOREIGN PATENTS Number Country Date 595,332 France Sept. 30, 1925 493,575 England 1937 

